However, when I do M-x slime in from Emacs I get the error: "Specified program for new process is a directory". I'm not sure what this means and extensive googling hasn't produced any solid results yet. Any help out there would be most appreciated. Thanks.

The inferior-lisp-program must contain a path of the program executable. In your snippet it is a directory, like the error message states. And it is the directory of the support files, not the executable, which should be either under some bin hierarchy, or wherever you installed the implementation.